1. Field of the Invention
The invention relates to a slider for use in a magnetic recording apparatus or the like and a method of working a slider. More particularly, the invention relates to a slider, which is formed by simultaneously multi-bonding many sliders on one substrate and then individually separating the sliders and which requires smoothness of the side and front surfaces thereof, and a working method for cutting the sliders and thereby individually separating the sliders.
2. Description of the Related Art
A slider for a magnetic head for use in a magnetic recording apparatus such as a hard disc driver (hereinafter referred to as HDD) is manufactured through steps generally shown in FIGS. 14A to 14F, for example.
First, a plurality of devices 1 such as a transducer having a function of writing/reading information as the magnetic head is multi-bonded on a substrate 2 such as a ceramic substrate or a silicon wafer (see FIG. 14A).
Then, the substrate 2 is cut so as to be rectangular in shape (see FIG. 14B). Then, the rectangular substrate 2 is further sliced into bars, each of which has a horizontal array of about ten or more devices 1, and bars 3 are individually separated from one another (see FIG. 14C). Heretofore, such cutting has been generally performed by the use of a diamond peripheral cutting edge. Then, each of the separated bars 3 is stuck on a suspension 4 that is a jig, with wax (not shown) or the like (see FIG. 14D). Sticking is adapted to be temporary bonding such that the devices 1 can be separated from the suspension 4 after the devices (sliders) 1 are completely individually separated from one another.
Then, each of the devices 1 arrayed on the bar 3 is worked as the slider. That is, a head slider surface is ground, structures functioning as the slider such as a groove for determining a width of a slider rail and a bleed slot surface are worked, and a head levitation surface, i.e., a slider rail surface is polished so as to have predetermined surface roughness of 0.05 xcexcm or less, for example. Furthermore, an air inlet for functioning as an air bearing surface (hereinafter referred to as ABS) of the slider rail surface is tapered (see FIG. 14E).
After the structure of a principal part of the slider is thus formed, sliders 6, each of which comprises each of the devices 1 worked in a unit of the bar 3, are separated one by one by cutting the bar 3 at a boundary between adjacent sliders 6 (see FIG. 14F). Heretofore, cutting for separating has been also generally done by the use of the diamond peripheral cutting edge.
Then, chamfering (so-called blending) takes place (not shown). In order to prevent the slider from damaging the surface of a magnetic recording medium (a magnetic disk) at the time of contact start/stop when the slider is mounted as a slider head and used in the HDD, chamfering is applied to more particularly an edge of the slider rail surface which is likeliest to contact the surface, additionally an edge line portion which is likely to contact the surface of the magnetic recording medium (the magnetic disk) and so on. Heretofore, the slider for the magnetic head for use in the magnetic recording apparatus such as the HDD has been manufactured through such a manufacturing process.
In the above-described step of working the slider for the magnetic head of the related art, chippings of about 1 xcexcm to 5 xcexcm are, however, produced more particularly at the edge where the surface of the ABS crosses a cut surface obtained by a diamond sharp edge grinding wheel and the edge where a rear surface opposite to the ABS crosses the cut surface obtained by the diamond sharp edge grinding wheel.
The chippings have a problem. Similarly to contamination such as dust, the chippings peel off the slider due to vibration, shock or the like during the use of the HDD, and thus the chippings damage the surface of the magnetic disk as the contamination or cause malfunction such as a read/write error resulting from thermal asperity.
More particularly, in recent years, a further increase in an information recording density has been strongly demanded. The increase in the information recording density requires a further reduction in an amount of magnetic spacing by more precisely controlling and further reducing a height of levitation of the slider from the recording medium. An approach of reducing a conventional height of levitation of about 40 nm to 50 nm by more than half, i.e., to about 10 nm to 20 nm and others have been also proposed. In order to realize the reduced height of levitation with high precision, it is therefore strongly demanded that the ABS is formed with higher accuracy of dimension.
There is a tendency to further reduce the height of levitation of the slider. However, even particles finer than conventional particles enter into a fine gap. Thus, the particles are likelier to damage the surface of the magnetic disk and the surface of the slider than the conventional particles.
When chippings as described above are at the edge line portion where the surface of the ABS crosses the cut surface obtained by the diamond sharp edge grinding wheel, when the edge portion itself has an acute angle, or when malformation due to asperities whose edge has an acute angle occurs at the edge, a contact of the edge with the surface of the magnetic recording medium (the magnetic disk) causes damage to the surface of the magnetic recording medium.
The HDD of the related art is manufactured in a clean room whose cleanness is comparable to the cleanness of class 100 or more for a process of manufacturing LSI in order to prevent contamination from entering the HDD at time of manufacturing. Moreover, an air filter is included in the HDD so as to cope with mainly external contamination. Such an approach allows coping with an entry of contamination during manufacturing and an entry of external contamination.
However, during manufacturing, the contamination produced by peeling of chippings as described above adheres to the cut surface still in the form of chipping. Thus, the chippings are not recognized as a cause of failures. Thus, the chippings are likely to cause malfunction at the time of an actual use of the HDD, but the chippings are not checked and are overlooked. At the time of the actual use of the HDD, the slider having the adhering chippings makes a relative movement over the nearly overall surface of the magnetic disk. Thus, the slider is always located on or near the magnetic disk whenever the chippings peel off. That is, almost all the particles of the peeling chippings always drop onto and adhere to the magnetic disk. Consequently, there is a problem that the particles produced by the peeling of the chippings are extremely likely to damage the surface of the magnetic disk or cause the read/write error as the contamination.
Thus, the chipping or the edge portion having acute angle causes various problems. In order to solve such problems, it is extremely important to chamfer more particularly the edge of the slider. A blending method using a lapping tape disclosed in Japanese Patent Application No. Hei 10-104235 and a method of rounding counters by ion milling are proposed as such a chamfering method.
The method using ion milling is that a shallow groove is previously formed in the edge or corner of an outline of the slider and the edge or corner is etched by using ion milling method. The edge or corner is etched not only vertically but also horizontally. As a result, the edge or corner is rounded, so that R (a radius of curvature) is as small as about 2 xcexcm to 3 xcexcm.
However, the method using ion milling has a problem of redeposition unique to the method. That is, even though ion milling method is used in order to remove chippings, redeposition occurs due to ion milling and redeposit peels off as new particles. Consequently, the method using ion milling has a fatal problem that the particles cause the same problem as the problem caused by chippings.
Moreover, other polishing methods are proposed. In a cutting method using a conventional grinding wheel, in order to eliminate the roughness of each cut surface of the outline of the slider and the chippings, the final cut surfaces of each of the individual sliders separated must be polished or subjected to other processes after the sliders are completely cut into the individual sliders. That is, protrusions of about 2 nm to 10 nm are produced at the edges of the cut surfaces of the sliders individually separated. Moreover, chippings of 1 xcexcm to 5 xcexcm are produced at the edges where the cut surface crosses the ABS. Therefore, the removal of protrusions and chippings requires polishing each edge of each slider. Polishing the edges takes place after separation of the sliders. A technique of thus individually polishing the sliders is proposed in Japanese Patent Laid-open No. Hei 6-282831, for example.
However, a step of lapping each of the cut surfaces of each slider after individually separating the sliders is extremely complicated, and thus the time required for the step is long. That is, in a conventional method in which the individual sliders separated is polished by lapping, a step of attaching each of the individual sliders to a lapping apparatus and lapping four side surfaces of each slider, i.e., the cut surfaces of each slider is an extremely complicated step. Thus, the conventional method has a problem that a throughput of the step is inefficient and thus the step requires a long time.
Moreover, in a lapping method, a depth of chamfering and polishing of the edge generally has a limit of up to about 5 xcexcm, and thus the depth is substantially difficult to be more than 5 xcexcm. When an attempt is made to further reduce the depth of polishing, the lapping method for mechanically polishing the surface cannot avoid the contact of the tape with the ABS of the slider and a slider body (more particularly, a magnetic pole portion or the like). As a consequence, there is a problem that the ABS and the slider body are scratched during polishing.
The invention is designed to overcome the foregoing problems. It is an object of the invention to solve a problem of damage to a recording medium such as a magnetic disk due to more particularly an acute edge line of an edge and harmful protrusions or chippings, thereby providing a slider and a method of working a slider which are capable of implementing a magnetic head that is available with high reliability without causing the damage to the magnetic disk and a read/write error when the magnetic head, for example, is incorporated and used in the HDD.
A slider of the invention is a slider having a polyhedral outline and having a surface facing a magnetic recording medium, wherein at least one of edges of the outline on the periphery of the surface facing the magnetic recording medium is chamfered into a concave curved surface.
In the slider, the edge on the periphery of the surface facing the magnetic recording medium is chamfered into the concave curved surface. Thus, the surface is an extremely smooth surface having no chipping or protrusion. Moreover, the edge on the periphery of the surface of the slider facing the magnetic recording medium is formed into the concave curved surface in cross section. Thus, even when the slider is inclined to the surface of the magnetic recording medium, it is possible to reduce the probability of strong contact of the slider with the surface of the magnetic recording medium.
More particularly, a cross-sectional shape of the edge of the slider of the invention is suitable for the cross-sectional shape of the edge of the slider which has more severely required satisfying hydrodynamic performance in recent years. If the slider assumes an inclined posture toward the magnetic recording medium due to some external perturbations or the like, the edge of the slider tends to move closer to the surface of the magnetic recording medium. However, in the slider of the invention, the edge has the concave curved surface which is hollowed like an inverted R in cross section. Thus, a dimension of the hollowed portion permits reducing the probability of contact of the slider with the surface of the magnetic recording medium. Moreover, the edge having the concave curved surface shaped like the inverted R in cross section is formed on the periphery of the surface facing the magnetic recording medium. Thus, in the slider of the invention, the cross-sectional shape of the edge allows pressure to be generated on the edge in the direction in which the slider is separated from the surface of the magnetic recording medium, i.e., in a positive direction.
In the slider according to the invention, even if the slider is inclined to the surface of the magnetic recording medium due to some external perturbations, the slider has such a structure that the edge of the slider exerts a force in the direction in which the edge is separated from the surface of the magnetic recording medium. Thus, it is possible to actively avoid a strong contact of the slider with the surface of the magnetic recording medium.
Furthermore, the edge of the surface facing the magnetic recording medium has the concave curved surface having the inverted R shape in cross section. Thus, the concave curved surface functions so as to decelerate airflow colliding with the concave curved surface and then direct the airflow in a horizontal direction, i.e., in the direction parallel to the magnetic recording medium (or the facing surface of the slider facing the magnetic recording medium). That is, for example, even when dust entering from the outside air or other particles is suspended over or adheres to the surface of the magnetic recording medium and the slider moves close to the surface, the edge of the slider according to the invention allows horizontally flowing the dust or particles as well as the airflow just like a fender. Thus, it is possible to prevent the dust or particles from entering into a gap between the magnetic recording medium and the slider. As a result, it is possible to avoid damage such as scratches on the surface of the magnetic recording medium, the surface of the slider or a magnetic head portion due to the dust or particles.
A method of working a slider of the invention having a polyhedral outline and having a surface facing a magnetic recording medium, for chamfering into a concave curved surface at least one of edges of the outline of the slider on the periphery of the surface facing the magnetic recording medium comprises a polishing step of bringing a wire saw into contact with the at least one edge and then pressing the wire saw against the slider while sliding the wire saw in a longitudinal direction, thereby polishing a surface in contact with the wire saw and chamfering the contact surface into the concave curved surface.
Another method of working a slider of the invention having a polyhedral outline and having a surface facing a magnetic recording medium, for chamfering into a concave curved surface at least one of edges of the outline of the slider on the periphery of the surface facing the magnetic recording medium comprises: a multi-bonding step of forming an array of a plurality of sliders on one substrate; a supporting step of allowing a suspension to support the sliders on a rear surface opposite to a front surface of the substrate on which the sliders are multi-bonded; a cutting step of cutting a boundary for individually separating the sliders, across the overall thickness of the substrate along the thickness of the substrate from the front surface of the substrate, at least without completely cutting the suspension; and a polishing step of bringing a wire saw of a diameter greater than a width of a portion cut by the cutting step into contact with the cut portion and then pressing the wire saw against the slider while sliding the wire saw in a longitudinal direction, thereby polishing a surface in contact with the wire saw and chamfering the contact surface into the concave curved surface.
Still another method of working a slider of the invention having a polyhedral outline and having a surface facing a magnetic recording medium, for chamfering into a concave curved surface at least one of edges of the outline of the slider on the periphery of the surface facing the magnetic recording medium comprises: a multi-bonding step of forming an array of a plurality of sliders on one substrate; a notching step of cutting a notch at a boundary for individually separating the multi-bonded sliders to some midpoint of a thickness of the substrate along the thickness of the substrate from the front surface of the substrate; and a polishing step of bringing a wire saw of a diameter greater than a width of the notch into contact with the notch and then pressing the wire saw against the slider while sliding the wire saw in a longitudinal direction, thereby polishing a surface in contact with the wire saw and chamfering the contact surface into the concave curved surface.
In the method of working a slider of the invention, the notch is previously cut to some midpoint of the thickness of the substrate or the substrate is further cut across the overall thickness of the substrate, and then the wire saw is brought into contact with the notch. Thus, the notch serves as a guideline and guides the wire saw to an appropriate boundary, i.e., a polishing position by self alignment. Therefore, polishing can take place at a precise position.
Moreover, the edge thus polished has such a concave curved surface in cross section as can implement performance suitable for the slider, and the edge has an extremely smooth surface having no chipping or protrusion. Moreover, a dimension of a portion to be chamfered and a radius of the inverted R of the concave curved surface of the cross section of the portion can be freely selected (set) in accordance with the radius of the wire saw to be used.
Furthermore, in the method of working a slider of the invention, polishing is performed by the use of the wire saw, and thus the polished surface has the concave curved surface in cross section as described above. In a process of manufacturing the slider having a rail shape as an ABS, this is more suitable for the formation of the so-called two-stage structure, i.e., a structure in which a side surface of the rail of the ABS is formed inward by a predetermined distance from the side surface of the slider. Moreover, a distance between the side surface of the rail of the ABS and the side surface of the slider in the two-stage structure can be freely selected (set) in accordance with the radius of the wire saw. The working method of the invention having many advantages as described above is a very simple working method which is feasible without the need for any complicated step.
In the method of working a slider of the invention, the polishing step may further include the step of bringing the wire saw into contact with a corner at which the edges of the slider cross each other, with the edge of the slider inclined along a length of the wire saw, and then pressing the wire saw against the corner of the slider while sliding the wire saw along the length of the wire saw, thereby polishing the surface in contact with the wire saw and chamfering the contact surface so that the contact surface may have the concave curved surface in cross section.
Thus, polishing takes place with the slider inclined along the length of the wire saw, thereby making it possible to polish, in particular, the corner of the slider and to chamfer the corner so that the corner may have the concave curved surface in cross section.
Moreover, in the method of working a slider of the invention, the polishing step may be performed through the use of slurry containing abrasive grains having a particle diameter of 5 xcexcm or less and the wire saw.
That is, an empirical rule that a damaged layer and a chipping produced near the edge at the time of cutting of the slider are both 5 xcexcm at the maximum has been heretofore obtained from previous practical manufacturing experience. It is therefore desirable that the substrate is cut by the wire saw by using the slurry containing abrasive grains having a particle diameter of 5 xcexcm or less in order to control a stock allowance equal to or less than 5 xcexcm, i.e., a size of the damaged layer and the chipping. However, the invention is not limited to this example. In consideration of a qualitative tendency as described above, the particle diameter of the abrasive grain for use in the slurry can be appropriately determined within a range of a particle diameter of 5 xcexcm or less so that the particle diameter can be adapted to required smoothness and precision in dimension of cut.
Powders of diamond, sapphire or the like for a general abrasive grain can be used as a material of the above-mentioned abrasive grain. When the slurry is not used, the wire saw having abrasive grains deposited to a wire itself, such as a diamond-electrodeposited wire saw, can be used.
The suspension for supporting the sliders on the rear surface thereof may be joined to the rear surface of the substrate in such a manner that the overall surface of the suspension is in contact with the rear surface of the substrate. Alternatively, the suspension may be joined to only devices or sliders so as not to be joined to a cutting allowance between the devices or the sliders, thereby supporting the devices or the sliders by only the joint portions. Moreover, temporary bonding using an adhesive or temporary support by applying a negative pressure such as an adsorptive method may be adopted as a method of supporting the devices or the sliders.
Moreover, in the method of working a slider of the invention, the devices or the sliders may be removed from the suspension after the polishing step. Alternatively, for example, the suspension is made of an insulating material and the substrate is cut together with the suspension into the individual devices or sliders, whereby the insulating suspension can be used as an insulating layer in each device or slider finally obtained. Thus, the suspension may be also used as a part of a structure of each of the devices or sliders like the insulating layer, without being removed from the individual devices or sliders.
Other and further objects, features and advantages of the invention will appear more fully from the following description.